406 PHYSIOLOGY. 



of the radial artery. From this it would seem that the juice has a 

 distinct action upon the vascular system. 



Whether the gland possesses the function of destroying toxic 

 products of metabolism which would otherwise tend to accumulate 

 in the blood is a point not yet understood. 



Experiments have shown that at least a part of the thyroid 

 gland must be allowed to remain after operations upon this gland. 

 Otherwise, cachexia will follow. 



' The thyroid contains two albuminous bodies, the one containing 

 iodine, the other having phosphorus. The first one has the char- 

 acter of a globulin and has received the name of thyreoglobulin and 

 by reagents is changed into iodothyrin. The thyroid also contains 

 choline, which depresses the heart and lowers blood-pressure. 



Fig. 147. Effect of Iodothyrin on Intestinal Peristalsis. 

 It increases the extent of the peristaltic movements. 



Hutchinson states that "if the presence of iodine in iodothyrin 

 is essential to the activity of this substance, it is not so in virtue of 

 its being iodine, but owing to the form of organic combination in 

 which it occurs/' It is estimated that the normal thyroid gland 

 contains approximately ten times as much iodine as the hypertrophied 

 glands of patients suffering from exophthalmic goiter. The thyroid 

 seems to possess a peculiar affinity for iodine. 



While our knowledge of the thyroid has been considerably 

 extended by reason of modern research, there yet remains much 

 that is very obscure. 



Thyroid by the mouth reduces weight by an increase of the 

 intake of oxygen and the output of carbon dioxide. This excessive 

 burning of fat produces water, thus causing increased secretion of 



